The National Security Agency must be more accountable and transparent to the US public about its operations following the furore caused by the leak of top-secret files by Edward Snowden, Barack Obama’s nominee to lead the agency said on Tuesday.

However, vice-admiral Michael Rogers offered no new concessions on the policy of mass data collection exposed by Snowden, the former NSA contractor whose unprecedented whistleblowing prompted a global debate about the nature of government surveillance.

Rogers told the Senate armed services committee that he had learned from the Snowden saga that, as NSA director, he would “have to be capable of communicating in a way that highlights what we are doing and why to the greatest extent possible”. He was appearing before the committee as the nominee to lead the US military’s Cyber Command and, if confirmed, will lead both agencies.

“I believe that one of my challenges as the director, if confirmed, is: how do we engage the American people, and by extension their representatives, in a dialogue in which they have a level of comfort as to what we are doing and why?” he said.

He declined an invitation to describe Snowden as a “traitor”. And under prickly questioning from John McCain, Rogers also suggested that the NSA needed to be more forthcoming if it breached the rules governing its activities.

“We have to ensure strict accountability on the part of the National Security Agency,” said Rogers. “We have to make sure that we do, in fact, follow those processes appropriately, and when we make a mistake, if we fail to meet those requirements, that we’re very up front about how and the why.”

He also agreed with McCain that “a select committee to investigate this entire issue” should be convened by members of congress in response to the wide range of issues raised in the past nine months.

Yet Rogers, a 32-year US navy veteran, offered a robust defence of the NSA’s surveillance activities and promised to develop a more active American policy of “deterrence” against adversaries in cyberspace.

He complained that plans announced by Obama amid intense criticism in January to transfer the storage of bulk telephone records to an independent body would complicate the NSA’s operations and cost significantly more money.

Stressing that he supported Obama’s plan, Rogers said in written testimony before his appearance: “If a private third party holds the data, I expect it would be at greater expense and could introduce other complexities.” He warned users that telephone companies may need to “alter their procedures in ways that raise new privacy concerns”.

Asked what capabilities the NSA would need to keep after Obama’s promised “transition” away from the use of section 215 of the US Patriot Act to justify the harvesting of vast amounts of metadata from American telephone users, Rogers appealed for similar powers.

“I believe that we need to maintain an ability to make queries of phone records in a way that is agile and provides results in a timely fashion,” he said. “Being able to quickly review phone connections associated with terrorists to assess whether a network exists is critical.”

Rogers told senators that he also had “concern” about the idea of leaving bulk metadata with the phone providers themselves, forcing intelligence agencies to obtain a court order compelling them to produce records relating to individual suspects.

Saying he doubted whether “such an arrangement would produce records in a timely fashion”, Rogers then repeated his earlier statement: “Being able to quickly review phone connections associated with terrorists to assess whether a network exists is critical.”

And he stressed that even if section 215 were allowed to expire next year, the NSA would be able to maintain similar capabilities for obtaining telephone records if “existing authorities were modified to enable more flexible acquisition of such records”.

In his written submission Rogers also repeated a suggestion made previously by Obama and a string of other senior US officials that the “section 215” program might have helped US spies who failed to intercept a phone call made by Khalid al-Mihdhar, one of the September 11 hijackers, from California to an “al-Qaida safe house in Yemen”.

His claim was struck down by Senator Mark Udall, Democrat of Colorado, who has consistently objected to the repeated use of this case in particular by security officials in their attempts to justify the program.

“I’m concerned by the implication that somehow the section 215 program could have prevented 9/11,” Udall told Rogers. “As the 9/11 commission pointed out, the CIA knew about al-Mihdhar, but did not tell the FBI. So the argument that business records data could have been the key to identifying al-Mihdhar doesn’t stand up in my view.”

During Tuesday morning’s hearing Rogers repeatedly declined to answer questions about the NSA on the basis that he had not yet joined the agency and that there were many details relating to its operations of which he was not aware.

However he appeared to surprise Senator Ted Cruz by declining to agree that every American was protected against unwarranted searches of their information by the fourth amendment to the US constitution unless they were the subject of “individualised suspicion”.

“I don’t know that I would make a blanket statement,” said Rogers. “I’m not a lawyer … that’s not my area of expertise”.